Influence of rotation on the metal rain in a Hadean magma ocean

Abstract

AbstractToday, it is widely accepted that during its early evolution, the Earth experienced a magma ocean that covered most of its surface. The separation of metal from silicate was much facilitated in the environment of such a magma ocean. The differentiation mechanism is known as the “metal‒rain scenario”. Our study will focus on the settling dynamics of these metal droplets. Because of the low viscosity of molten silicate and a higher rotation period of the Earth at that time the rotation has a potentially strong influence on the dynamics of the magma ocean. We use numerical 3D fluid simulations to analyze the combined effects of strong rotation and convection on the settling of the iron droplets. We show that the influence of rotation on the settling depends on the latitude. At the poles, the influence of rotation is only marginal. At the equator, three different scenarios can be distinguished. First, at low rotation rates, the particles form a dense layer at the bottom. Second, for strong rotation, the particles stay mostly suspended and layers form in the temperature field. Third, at higher rotation rates, the particles form a ribbon‒like structure in the middle of the box. The influence of rotation on the iron droplets may lead to a scenario where part of the iron is kept in the mantle instead of transported to the core. This would have a strong influence on the later states of the differentiation process and the amount of siderophile elements in the mantle.